A valve, tap or faucet which regulates the flow of liquid or gas through a pipe.
A main shutoff for water to a home from a municipal supply. Usually these valves exist in pairs, one outside the property boundary and one inside the property boundary.
To control the gas pressure in (an oil well) by keeping the well closed in and the gas confined except during set intervals when the oil is flowed or pumped.
A type of electron tube that controls electron current through vacuum between electrodes within a sealed container, usually of glass or metal and often designed to be easily installed in and removed from the equipment in which it is used.